Think I know what's going on. I was loading remot3.it from my Windows 10 PC Firefox bookmarks list and the URL was
When I checked what the Raspberry pi was using it was
I have just checked the latter from my Windows PC and all is now good, clearly the URL has changed since I first accessed remot3.it and saved the bookmark.
Apologies if I have led you up the garden path and thanks for your time & assistance.